98 Honda Accord LX. I scanned the codes and found codes 135, 141, bad heater core for the oxygen sensor bank 1 & 2. I replaced both oxygen senosrs (bank 1 and 2) with denso OE sensors and cleared the codes with a scanning tool. Codes remained, so I brought the car to a honda dealer and they said I need two new honda oxygen sensors. While I didn't believe this would correct the problem I replaced with two honda oxygen sensors with no luck. Anyone have any thoughts on what to check next?

 

Well the factory repair manual gives several things to measure when you get those codes. Sounds like you and the dealer went right to the sensor-replacement without actually diagnosing.

I'm pretty sure Honda sensors are made by Denso, so you had already done the same thing the dealer wanted to do.

Most times the problem IS a bad sensor. Occasionally the problem is in the car's wiring harness.

 

I would start checking the wires for cuts in the wires, etc.

Was this car bought from someone else? If so, maybe they did some tampering of the O2 sensor wires, like adding resistors, etc. to try to fool the ECU.

 

The "Honda" sensors actually had denso stamped on them. We brought the car to the dealer figuring they were the experts and would be able to diagnose the problem. I was wrong about that, they wanted us to spend $700 on two sensors we already replaced.

We did buy the car used. I traced the wires back near the fire wall and didn't see any cuts in the wiring. I'm guessing I need to start checking fuses and relays etc.?

 

This will be interesting to find out what is actually wrong with the car as this code pops up often....

I'll be watching this thread.

 

Is this a 4 or 6 cylinder accord?

 

It's a 4 cyclinder. Does anyone know what the honda manual suggest to check?

 

You can download one. Search the DIY section for a listing of a few places to get one.